Transition metal sulfide clusters below the cluster-platelet transition: Theory and experiment

The structural and electronic properties of neutral and anionic molybdenum sulfide clusters with the composition Mo(3)S(n) (n = 0-12) were studied by density-functional calculations. The theoretical results are confirmed by a comparison with photoelectron spectra of the corresponding W(3)S(n)(-) anions providing experimental values for the vertical detachment energies (VDEs) and the highest occupied (HOMO) and lowest unoccupied (LUMO) gaps. For sulfur contents up to n = 9 the clusters are composed of a central Mo3 unit, which is decorated by bridging, terminal, and three-fold coordinated S atoms. For n > 9, a cleavage of the Mo3 center is observed. The formation of disulfide like ions is found for Mo(3)S(9) and larger species. In accordance with investigations of MoS(n), Mo(2)S(n), and Mo(4)S(n) clusters, the heat of formation and the VDE reaches a maximum in the sulfur-rich region beyond the composition Mo:S = 1:2. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim